No downcast for unhashable

Author: youknowone

vm/src/types/slot.rs

@@ -499,8 +499,11 @@ impl<T> Hashable for T
 where
     T: Unhashable,
 {
-    fn hash(_zelf: &PyRef<Self>, vm: &VirtualMachine) -> PyResult<PyHash> {
-        Err(vm.new_type_error(format!("unhashable type: '{}'", _zelf.class().name())))
+    fn slot_hash(zelf: &PyObjectRef, vm: &VirtualMachine) -> PyResult<PyHash> {
+        Err(vm.new_type_error(format!("unhashable type: '{}'", zelf.class().name())))
+    }
+    fn hash(_zelf: &PyRef<Self>, _vm: &VirtualMachine) -> PyResult<PyHash> {
+        unreachable!("slot_hash is implemented for unhashable types");
     }
 }